In telecommunications, a diversity scheme refers to a method for improving the reliability of a communication by using two or more communication channels with different characteristics. Diversity plays an important role in combatting fading and co-channel interference and avoiding error bursts. It is based on the fact that individual channels experience different levels of fading and interference. It is known to use either transmit diversity scheme or a receive diversity scheme. In the transmit diversity, a signal is transmitted via multiple communication channels over air interface, and in the receive diversity, the signal is received via multiple communication channels over the air interface. Therefore, multiple versions of the same signal may be transmitted and/or received and combined in the receiver(s) system(s) having analog and digital functionalities and needed amount of software (SW) algorithms for fulfilling the systems requirements. Diversity techniques may exploit the multipath propagation, resulting in a diversity gain.
In radio communication networks, such as for example in the evolved high speed packet access (HSPA+), in the long term evolution (LTE), in the LTE-Advanced (LTE-A) of the 3rd Generation Partnership Project (3GPP), in the code division multiple access (CDMA) and in the time division synchronous CDMA (TD-SCDMA) systems, a multiple-input and multiple-output (MIMO) technique may be used. In the MIMO, multiple antennas at both the transmitter and receiver are employed to improve the communication performance. The MIMO may be applied in generating transmit and/or receive diversity in network elements and terminals. Furthermore, the MIMO may be applied in increasing data/payload throughput of the system (MIMO gain/performance) as the need of retransmissions may be minimized. Further, different signals may be transmitted simultaneously in different data streams. However, in order to obtain increased reliability or throughput, low correlation between the applied MIMO antennas is required. Thus, it is important to provide a solution for efficiently using the diversity schemes with multiple antennas.